phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 2

INSERT INTO forum_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('c73d81f0a47a1030d9f98f9a79195d5c', -1, 1417245741, 1417245741, '365159b6', -9, 0, 0)

Line : 187
File : sessions.php